1. Field of the Disclosure
The present disclosure relates to magnetic head devices including magnetic sensors that are supplied with a sensing current from shield layers, including tunneling magnetoresistive (TMR) sensors and current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) sensors. In particular, the disclosure relates to a magnetic head device having soldered conductive pads electrically connected to shield layers.
2. Description of the Related Art
A magnetic head device for use in a hard disk drive, for example, has a magnetic sensor mounted on a slider and conductive pads arranged on an end surface of the slider. The magnetic sensor operates by a magnetoresistive effect. The slider is supported by a leaf spring called a flexure. The flexure, in turn, is mounted on a support member called a load beam. The slider is disposed opposite a surface of, for example, a hard disk and is supported so that the slider can be moved relatively freely as the flexure is deformed.
Conductive patterns are formed on surfaces of the load beam and the flexure with an insulating layer disposed therebetween. Electrodes are formed integrally with the conductive patterns on the surface of the flexure. The electrodes are disposed near the conductive pads arranged on the end surface of the slider.
With the slider fixed to the flexure by bonding, the conductive pads of the slider are connected to the electrodes of the flexure using a molten metal. A typical example of the molten metal used is a lead-free, tin-silver alloy solder. Examples of the related art are disclosed, for example, in Japanese Unexamined Patent Application Publication Nos. 2004-152393 and 2004-164813.
If the magnetic sensor is a TMR sensor, a magnetoresistive sensor utilizing a tunneling effect, or a CPP GMR sensor, a magnetoresistive sensor in which a sensing current flows perpendicularly, the magnetic sensor is disposed between a pair of shield layers with the top and bottom surfaces thereof in contact with the shield layers. The shield layers are connected to lead layers so that a sensing current flows perpendicularly from the conductive pads to the magnetic sensor via the lead layers and the shield layers.
When the conductive pads of the slider are bonded to the electrodes formed on the surface of the flexure using a molten metal, the conductive pads are heated to high temperature during the bonding and can instantaneously reach a temperature exceeding 300° C. The heat is then transferred from the lead layers to the shield layers, and accordingly the sides of the magnetic sensor are heated to high a temperature.
In addition, the areas of the shield layers in contact with the top and bottom surfaces of the magnetic sensor are larger than those of electrode layers in contact with the sides of a typical current-in-plane (CIP) GMR sensor. The heat is therefore readily transferred from the shield layers to the magnetic sensor. If the magnetic sensor reaches a high temperature exceeding, for example, 230° C., its pinned magnetic layer exhibits unstable magnetization, which can decrease magnetic sensitivity. Furthermore, the heat can cause variations in the magnetic domains of the shield layers. Such variations can result in generation of superimposed noise and unstable read output.